It is widely acknowledged that early child development is sensitive to the social environment in which it occurs, although the details of the relationship between the environment and child development are not well understood. The proposed research is a short-term longitudinal study of the influence of the social environment on early mother-child conversation and the effects of that early language experience on children's language development. The participants will be 30 working-class and 30 upper-middle-class mothers and their 16-22 month-old children. Interaction will be recorded in the home in four different naturalistic settings -- dressing, feeding, bookreading, and play. Video-taped records of mother-child interaction will be collected twice over a two-month period of language growth which includes the beginning of combinatorial speech. Properties of mother and child speech coded from transcripts of these interactions will provide the data for two proposed studies. Study 1 investigates whether mothers' speech to their children varies as a function of setting or social class and whether such variation is relevant to children's language growth. Study 2 investigates whether different environments support language development in different ways by comparing the influences of mothers' speech on their children's language growth in the two social classes. The objective of this research is to describe the range of linguistic interactions children experience in different social environments and the influences of those environments on language development. That description should provide a basis for evaluating competing hypotheses concerning how the child's learning mechanisms use the experiences provided by the child's social environment in acquiring language. This research should also provide a basis for optimizing the environmental supports for language acquisition in cases of language delay.